1. Field of the Invention
The present invention relates to systems and methods for performing refractive laser surgery on the eye, and, more particularly, to such systems and methods that adaptively modulate sensed data on the basis of data from prior procedures.
2. Description of Related Art
In conventional refractive laser surgery a clinician typically modifies a prescription entered into the treatment system. Such modifications are based upon prior experience with outcomes achieved with that particular treatment system, and also upon experience with particular patient populations derived from, for example, demographic data. For example, a surgeon might enter a 2-diopter myopic treatment prescription for a patient diagnosed with 3 diopters of myopia if analysis of previous outcomes indicates a 50% overcorrection using this system for patients of a particular category. Such an empirical alteration of entered treatment parameters based upon previous experience is referred to as a nomogram adjustment. Nomograms are considered essential by the ophthalmic community because different clinicians employ different surgical techniques, operate under different environmental conditions, have distinct patient demographics, etc.
Conventional surgery involves a limited number of well-defined treatment parameters, principally spherical error, astigmatic error, astigmatic axis, optical zone size, and blend zone size. Thus it is relatively straightforward for a surgeon to develop nomogram formulas based on conventional clinical examinations before and after surgical procedures. In contrast, wavefront-guided customized treatments, such as that disclosed in commonly owned U.S. Pat. No. 6,270,221 B1, the disclosure of which is incorporated herein by reference, involve complex a mathematical description of the pre-operative aberration profile, which is transferred electronically to the treatment system.
Although such a precise wavefront description can in theory be modified empirically to yield a better outcome, typically clinicians are not skilled in the analytic interpretations of these mathematical parameters. In addition, at present there is no known convenient method for a surgeon to modify a wavefront-based prescription prior to a procedure such as laser surgery.
In currently used wavefront-based treatments, the raw wavefront data are modulated to generate a treatment profile in order to account for an apparent radial dependence in the effectiveness of ablative treatment on the corneal tissue. This, however, is currently applied identically in all treatments.
It is therefore an object of the present invention to provide a system and method for creating a nomogram for adaptively modulating sensed wavefront data based upon prior treatment outcomes.
It is a further object to provide such a system and method that are site-specific.
It is another object to provide such a system and method that are demographically based.
These and other objects are achieved by the present invention, one aspect of which is a method for refining a prescription for laser-ablation corneal treatment. The method comprises the steps of receiving a measured correction prescription for a current patient. Typically the prescription will have been obtained using a wavefront determination. The current patient will have associated with him/her a classification element for placing the patient in at least one particular category.
Next a database of treatment outcomes on a plurality of previously treated patients is accessed. The database contains, for each previously treated patient, at least one classification element and also comprises a preoperative wavefront-determined correction prescription and a postoperative visual profile. A difference between the preoperative correction prescription and the postoperative visual profile represents an over- or undercorrection resulting from the surgery.
Treatment outcome data are accessed from the database based upon possessing a classification element in common with the current patient. From these data, an average difference may be calculated between the preoperative prescription and the postoperative profile. This average difference is then used to adjust the current patient""s correction prescription to form an optimized prescription prior to performing the procedure.
Another aspect of the present invention includes a software package for performing the calculational steps outlined above.
A further aspect includes a method for creating a system for optimizing a prescription for laser ablation surgery, which includes the steps of forming a database of treatment outcomes as described above. A search engine resident on a processor is adapted to extract treatment outcomes based upon a classification element. Software is also provided for performing the calculational steps as outlined above.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.